Post by-pass heart surgery

My elderly (79 yr. old) mother recently had double by-pass heart surgery. She is very independent, so we have a nurse and a physical therapist that comes to see her several times a week at her home. My brother & his wife live very close by and visit her several times a day and at night. They bring her dinner every night. I live an hour away and visit her for hours at a time several days a week. And we have a neighbor (woman and her dh) who my mother adores who are also checking in on her. So she is getting lots of care and people checking in on her.

Her surgery went very well and her physical recovery seems to be going well. What we are having a problem with is her mental/emotional state of mind. Within days after her surgery, she was telling everyone that she wished she had died in surgery. My mother is a fighter and elected to have this surgery rather than have a heart attack or stroke. She has plans to have the veins in her legs stripped/cleared of the blockages because she has trouble walking and loves to travel. Her legs are now getting a lot more blood flow and she looks a lot better having some color to her skin after years of looking so pale from a lack of good circulation.

Her doctor said that depression and/or anxiety is common after this kind of surgery. I am wondering why. I have had 4 surgeries and never wanted to die or felt anxious after any of them. I was in a great deal of pain, but never felt like I wanted to give up. My mother says that she is not in any pain, but is just tired. She is slowly getting her appetite back and doing short spurts of activity, so she seems to be doing well physically.

What I am wondering ... do they stop the heart during surgery? I would assume so. That would mean that you are clinically dead for a few minutes, right? Is it possible that being dead somehow affects the brain or the emotions? I have heard of people being revived after being dead and they become depressed afterwards. I am wondering if my mother's heart surgery might be causing her to be depressed and have a desire to die. My brother and I are having a hard time convincing her to be a fighter. (She has always been a fighter until this surgery. She went into this surgery with high hopes for a better quality of life which we know she will have once she recovers completely.) We are baffled by her emotional state and we just don't know what to do to convince her to fight to recover. She just isn't showing any desire to get better and recover. It has us very worried.

Any insight into this type of surgery and recovery would be very much appreciated. Thank you! ~Becky~